1. Field of the Invention
This invention relates to light emitting devices, such as Laser Diodes (LDs) or others; photodetecting devices, such as PIN Photo Diodes (PINPDs), Avalanche Photo Diode (APD) or others; an optical electric integrated circuits(OEICs) which integrate optical active devices, such as LDs, LEDs, PINPDs, APDs, etc. and electric devices, such as amplifiers, drivers, FETs and others.
2. Related Background Art
Conventionally in, e.g., light emitting devices for this use, various devices have been made for the purpose of collecting radiation from diode chips by lenses or other means to improve the coupling efficiency to optical fibers or others, and the precision of aligning optical axes with those of the optical fibers or others.
The light emitting device of FIG. 24A (Japanese Patent Laid-Open Publication No. 139367/1987) comprises a diode chip 62 mounted on a can-type package 61, and a spherical lens 62 adhered to a light emitting surface 62a of this chip 62. The package 61 is sealed by a glass cap 64. The light emitting device of FIG. 24B includes another ball lens 66 attached to the center of the cap 64. The cap 65 is adhered to the package 61 to seal the chip 62 air-tightly to thereby make up a lens system on the optical axis of the chip 62.
The light emitting device of FIG. 25 (Japanese Patent Laid-Open Publication No. 139367/1987) comprises a stem 72 with a diode chip 71 mounted on, and a plastic cap 73 adhered to the stem 72 for air-tight sealing of the diode chip 71. A spherical chip coat 74 is applied to the side of the light emitting surface 71a of the diode chip 71, while an emission surface 73a of the plastic cap 73 is formed in a lens-shape to make up a lens system.
FIG. 26 (Japanese Patent Laid Open Publication No. 88377/1987) shows the conventional LED collimator (light emitting diode) for aligning optical axis with that of an optical fiber with high precision. This collimator comprises a stem 82 with a light emitting diode 81 mounted on, a stepped sleeve 83 adhered to the stem 82 for sealing the light emitting diode 81. In this stepped sleeve 83, a ball lens 84 at the middle portion thereof, and a restricted portion 85 is disposed on the front thereof. In this restricted portion 85 is fixedly inserted an optical fiber F.
FIG. 27 (Japanese Patent Laid-Open Publication No. 73786/87) shows the conventional light emitting device for enhancing the coupling efficiency with optical fibers.
This light emitting device comprises a frame 91 having the head 92 made of metal, such as aluminum, or others. A concave groove 92a is formed in the middle of the head 92. A light emitting diode 93 is rested in the concave groove 92a. The concave groove 92a has the wall formed in a curved surface. This curved face is a reflection surface 92b. These members are integrated by resin molding. Consequently diagonally horizontally reflected light which is usually loss light is reflected forward by the reflection surface 92b.
The emission surface 94a of the resin molding 94 is formed in a semisphere to function as a lens, so that radiation is converged there.
Thus, the reflection surface 92b decreases light loss to remove uneven luminance and enables the emission surface 94a to positively condense light.
The light emitting diode of FIG. 24 has the problem that the diode chip 62 is air-tightly packaged, which requires a number of parts, and its fabrication process is accordingly complicated. Besides the light emitting diode of FIG., 24B needs aligning the optical axis of the diode chip 62 with those of the ball lenses 63, 64, and in welding the cap 65 to the package 61, their positioning needs considerably high precision. The fabrication process is accordingly complicated, and resultantly its fabrication cost goes up.
In the light emitting diode of FIG. 25 as well, considerable precision is required in welding the plastic cap 73 with the lens system to the stem with the diode chip 71 mounted on, and the fabrication process is complicated.
In the light emitting device of FIG. 26, it is necessary to agree with good precision the optical axis of the light emitting diode 81 with the center of the end surface of an optical fiber F for the purpose of enhancing the coupling efficiency in adhering the stepped sleeve 83 with a restricted portion 85 for fixing the optical fiber F. This precision depends on a precision of positioning the stepped sleeve 83 to the stem 82. Accordingly considerable precision is required, which makes the fabrication process of the light emitting device complicated. This has incurred high fabrication costs.
In the light emitting device of FIG. 27, the portion for removing light loss, and the portion for positively condensing radiation are separately constituted. This makes the structure of the device and its fabrication process complicated. When the light emitting diode 93 is die-bonded, the head 92 of the frame 91 providing the reflection surface 92b is heated, adversely making the reflection surface 92b rough, with the result of lowered reflection efficiency.